The present invention relates to a home use video tape recorder and, more particularly, to a video tape recorder (hereinafter, referred to as a VTR) having a special demagnetizing function to execute a demagnetizing operation which is not accompanied with a recording operation.
Hitherto, as an apparatus for demagnetizing the recorded content on a magnetic tape at a high speed, as disclosed in JP-A-1-269203, a high-speed demagnetizing apparatus which demagnetizes the recorded signal while running a magnetic tape at a speed which is n times as high as a tape running speed in the normal reproducing mode has been proposed. As a demagnetizing method, the magnetic tape is run at the ordinary tape running speed at the initial stage of the start of the demagnetization, the recorded signal is demagnetized by three kinds of erasing heads comprising a full-width erasing head, a rotary erasing head, and an audio erasing head, and after the elapse of a predetermined time, the magnetic tape is run at a speed which is n times as high as the ordinary tape running speed, the erasing operation is executed by using only the full-width erasing head, and thereby enabling the high-speed demagnetization to be performed without causing a situation such that the recorded signal remains without being erased. Examples of the ordinary demagnetizing operation and the high-speed demagnetizing operation to which the ordinary demagnetizing operation is applied will now be described hereinbelow with reference to FIGS. 1, 2, and 3. FIG. 1 shows an example of a block diagram of a home use VTR. In FIG. 1, reference numeral 1 denotes a VTR; 2 a signal system block; 2a a video processing section; 2b an audio processing section; 2c a demagnetizing circuit section; 3 a power source section; 4 a microcomputer (hereinafter, abbreviated to a micom); 5 a character adding device; 6 a display section; 7 a driving system block; 8 a remote controller receiver; 9 a monitor; and 10 a remote controller (hereinafter, abbreviated to a remocon). FIG. 2 is a diagram showing a mechanism of the home use VTR. In FIG. 2, reference numeral 11 denotes a supply reel; 12 a fullwidth erasing head; 13 a magnetic tape; 14 guide posts to guide the magnetic tape so as to accurately keep a running path of the magnetic tape; 15 video recording/playback heads (CH-1/CH-2); 16 a rotary erasing head; 17 Hi-Fi audio recording/playback heads; 18 a rotary head cylinder; 19 an audio/control signal erasing head; 20 an audio/control signal recording/playback head; 21 a pinch roller; 22 a capstan; and 23 a take-up reel. FIG. 3 is a diagram showing track patterns recorded on the magnetic tape. In FIG. 3, reference numeral 24 denotes a CH-1 video track; 25 a CH-2 video track; 26 a linear audio track; and 27 a control track. In FIGS. 2 and 3, the magnetic tape 13 wound around the supply reel 11 is guided by the pinch roller 21 and the capstan 22 and is wound around, the take-up reel 23. In the tape path between the supply reel 11 and the take-up reel 23, the magnetic tape 13 is in contact with six kinds of heads 12, 15, 16, 17, 19, and 20 and a signal is erased, recorded, and reproduced. In the normal recording mode, on the magnetic tape 13 supplied from the supply reel 11, the signals on all of the tracks are first erased by the full-width erasing head 12, the video signal and the Hi-Fi audio signal are subsequently recorded by the video recording/playback heads 15 and the Hi-Fi audio recording/playback heads 17, the signals on the linear audio track 26 and the control track 27 are erased by the audio/control signal erasing head 19, and a linear audio signal and a control signal are finally recorded by the audio/control signal recording/playback head 20. In the case that video signals are recorded on the previously recorded video signals of a magnetic tape, the signals on only the video tracks (24 and 25) are erased by the rotary erasing head 16 instead of the full-width erasing head 12 for a few seconds just after the start of recording the video signals on the previously recorded video signals of the magnetic tape. In the playback mode, the above three kinds of erasing heads (full-width erasing head 12, rotary erasing head 16, audio/control signal erasing head 19) are made inoperative but only the above three kinds of recording/playback heads (video signal recording/playback heads 15, Hi-Fi audio recording/playback heads 17, audio/control signal recording/playback head 20) are made operative to thereby execute the reproduction. In FIG. 1, the micom 4 sends control signals to the driving system block 7, thereby controlling the tape sending operation and the mechanical operations such as cylinder rotations and the like. The micom 4 sends control signals to the signal system block 2, thereby controlling the switching operations of signal processes including the operations of the various kinds of heads. In addition to the above controls, the micom 4 also executes an ON/OFF control of the power source section 3, a character insertion control by the character adding device 5, and a control of the display section 6 of the VTR. Although the ordinary demagnetizing operation is executed only just before the recording operation, a special demagnetizing function is realized by executing the demagnetizing operation which is not accompanied with the recording operation. On the other hand, a high-speed demagnetizing function is realized by executing the special demagnetizing operation by setting the running speed of the magnetic tape to a speed which is n times as high as the ordinary running speed.
In the above conventional technique, nothing is considered with respect to the improvement of a use efficiency such that the special demagnetizing function is made operative for which tape position interval by which operation or the like.